1. Field of the Invention
The invention relates to a mobile terminal such as a mobile phone terminal to which an intelligent battery pack can be attached as power supply, and a charging system including the mobile terminal having the intelligent battery pack. Specifically, the invention relates to technology for charging a battery pack via a mobile terminal.
2. Description of the Related Art
In the related art, a mobile phone terminal utilizing a lithium-ion rechargeable battery as power supply generally incorporates a temperature detecting device such as a thermistor inside the battery pack containing the lithium-ion rechargeable battery for detecting temperature anomaly, specifically, for detecting the temperature exceeding the ordinary operating temperature range to monitor the temperature of the battery while charging.
FIG. 1 is a block diagram illustrating electric connections between a related art battery pack 2 and a mobile phone terminal 240. As illustrated in the figure, the battery pack 2 includes a battery plus terminal 231, a battery minus terminal 233, and a thermistor 232. A battery cell 20 is connected between the battery plus terminal 231 and the battery minus terminal 233. A switch 22 controlling charge and discharge of the battery cell 20 is connected between the battery cell 20 and the battery minus terminal 233. The switch 22 is controlled by a protection unit 21. A thermistor 23 is connected between the battery minus terminal 233 and the thermistor terminal 232. In the electric connection described above, a resistance value at the thermistor 23 varies with the temperature inside the battery pack 2, based on which voltage of a signal obtained by the thermistor 232 will be changed. The mobile phone terminal 240 is configured to monitor the voltage of the signal obtained by the thermistor terminal 232 and the temperature inside the battery pack 2.
Next, a configuration of the mobile phone terminal 240 is described. The mobile phone terminal 240 has three terminals 241, 242, 243 connecting to terminals in the battery pack 2, respectively. The plus terminal 241 is connected to the battery plus terminal 231 in the battery pack 2. The minus terminal 242 is connected to the battery minus terminal 233 in the battery pack 2. The thermistor connecting terminal 243 is connected to the thermistor terminal 232 in the battery pack 2. The mobile phone terminal 240 also has an external power supply input terminal 230 connecting the mobile phone terminal 240 with external power supply such as an AC adapter that transforms and rectifies commercial alternating power supply.
The mobile phone terminal 240 has a charge processor 210 controlling charging of the battery pack 2. The charge processor 210 is integrally formed, for example, of an integrated circuit (IC), and controls charging of a battery cell 52 inside the battery pack 2. When the battery cell 52 contained in the battery pack 2 is a lithium-ion rechargeable battery, the battery cell 52 is fully charged with combination of constant current charge and constant voltage charge. The charge processor 210 has a reference voltage output unit 201, current detecting unit 202, charge control unit 203, and temperature detector 200. The reference voltage output unit 201 applies reference voltage output to the thermistor connecting terminal 243 via a dividing resistor 204. When the mobile phone terminal 240 is connected to the battery pack 2, the reference voltage output by the reference voltage output unit 201 is divided between a dividing resistor 204 and thermistor 23, and the voltage at the dividing point thereof is detected by the temperature detector 200. The temperature detector 200 determines whether the detected voltage value exceeds the threshold, and transfers the resulting data to the charge control unit 203.
The mobile phone terminal 240 has a series circuit formed of a charge current detecting resistor 205 and charge control transistor 206 connected between the external power supply input terminal 230 and the plus terminal 241. The current detector 202 gauges the current flowing in the charge current detecting resistor 205 and transfers the gauged current data to the charge control unit 203. The charge control unit 203 controls a charge control transistor 206 based on the data transferred from the current detector 202 and temperature detector 200.
When the mobile phone terminal 240 charges the battery pack 2, the charge processor 230 retains the charge control transistor ON. When the mobile phone terminal 240 stops charging of the battery pack 2, the charge processor 230 turns the charge control transistor 206 OFF to disconnect electric connection between the external input terminal 230 and the battery plus terminal 241. When neither charge current detected nor temperature detected are normal, the mobile phone terminal 240 turns the charge control transistor 206 OFF to stop charging of the battery pack 2.
The mobile phone terminal 240 utilizing the battery pack 2 having such related-art configuration detects the temperature using the thermistor 23 inside the battery pack 2, which implies that analog signals are flowing in the termister terminal 232.
In the related-art configuration of the battery pack 2 shown in FIG. 1, the mobile phone terminal controls charging of the battery pack 2 based on the temperature detected inside the battery pack 2. However, an intelligent battery pack is now provided as a more sophisticated battery pack. Such an intelligent battery pack includes an electric circuit that manages the battery condition, and communicates with the mobile phone terminal. FIG. 2 is a block diagram illustrating electric connections between the related art intelligent battery pack 5 and a mobile phone terminal 240.
Description of components identical to those illustrated in FIG. 1 is omitted. A mobile phone terminal 240′ in FIG. 2 has a serial interface (SIF) 212 in addition to the components of the mobile phone terminal 240 in FIG. 1, via which a counterpart connected to the terminal 243 (i.e., intelligent battery pack 5) communicates with a central processing unit (CPU) 211 to control the components of the mobile phone terminal 240′. CPU 211 has a memory 213 connected thereto that stores computer programs and data. CPU 211 controls a liquid crystal display (LCD) 214 that displays various types of display, such as notification of the remaining battery capacity for the mobile phone terminal.
The intelligent battery pack 5 includes a fuel level gauge processor 50 (hereinafter referred to as “FG processor”) that gauges voltage, current, and temperature in the battery cell 52, and protection processor 51 that controls the processing of transferring the data from FG processor 50 to the mobile phone terminal 240′ and controls a switch 54 for charge and discharge of the battery cell. A current gauging resistor 53 and switch 54 are connected between the battery cell 52 and the battery minus terminal 233.
FG processor 50 gauges the voltage of one-cell battery 52 with a voltage gauge unit 500. FG processor 501 further gauges the temperature of one-cell battery 52 with a temperature gauge 501. FG processor 501 still further gauges potential at both ends of the current gauging resistor 53 with the current gauge 502 and gauge the current when charge and discharge current. A multiplexer 503 carries out time-division multiplexing on the obtained results, supplies the multiplexed data to an analog-to-digital converter 504 to convert the data into digital data, and then supplies to the resulting data to CPU 505. CPU 505 is connected to a memory 506 on which a computer program for control is recorded, and determines whether the obtained data is normal.
The results determined by CPU 505 is transferred to a level converter (L/S) 510 inside the protection processor 51 via serial interface (SIF) 507, and the level converter (L/S) 510 converts the results into the level of data adequate for transmitting it to the mobile phone terminal 240′ and output the resulting data to a thermistor data communication terminal 234.
As shown in FIG. 2, the intelligent battery pack 5 further includes the thermistor 23 that is connected between the thermistor data communication terminal 234 and the battery minus terminal 233.
In a case where the intelligent battery pack 5 having a configuration shown in FIG. 2 is connected to the mobile phone terminal 240′, the charge processor 210 is capable of controlling charging of the battery pack based on the temperature detected via the thermistor 23 in the mobile phone terminal 240′. Further, CPU 211 is capable of controlling discharge from the intelligent battery pack 5 based on the battery status detected by FG processor 50 inside the battery pack 5. In this case, communication between the battery pack 5 and mobile phone terminal 240′ is carried out using the thermistor terminal in the battery pack shown in FIG. 1 without modification; that is, the communication therebetween is relatively easily carried out with existing configuration.
Japanese Unexamined Patent Application Publication No. 2006-155922 discloses a configuration of the battery pack of this type.